New York City Mayor Michael Bloomberg is joined by Vice President Joseph Biden (left) and family members of victims of Sandy Hook school shooting during a news conference at City Hall in New York, on Thursday, March 21, 2013. The group demanded that Congress take action on commonsense gun reforms and pass legislation like background checks for all gun sales.

NEW YORK — New York City Mayor Michael Bloomberg, a staunch advocate of tougher gun control laws, will bankroll a $12 million national advertising campaign aimed at key members in the U.S. Senate, the mayor said in an interview with The New York Times published on Saturday.

The commercials to be run by Mayors Against Illegal Guns feature a hunter with a rifle, vowing to protect the right to bear arms and voicing support for comprehensive background checks “so criminals and the dangerously mentally ill can’t buy guns.”

The advertising campaign will run in 13 states to target specific members of the U.S. Senate during the upcoming Congressional recess, according to the organization, of which Bloomberg is a co-chairman.

Bloomberg, who leaves office in January after three terms as Mayor of New York, has championed gun control and been particularly outspoken since a gunman killed 20 students and six adults at a Newtown, Conn., elementary school in December.

Last week, he appeared at City Hall with parents of some of the Newtown victims and Vice President Joe Biden, who is spearheading the Obama administration’s efforts to curb gun violence.

The Times said Bloomberg, a self-made billionaire, would bankroll the ad campaign. A spokesman for the mayor could not be immediately reached to comment.

The ad campaign marks a push back against the National Rifle Association, the mayor said in the Times interview.

“The N.R.A. has just had this field to itself,” Bloomberg said. “It’s the only one that’s been speaking out. It’s time for another voice.”

The Senate is set to begin considering gun legislation when Congress returns from its Easter recess in the second week of April.

“These ads bring the voices of Americans — who overwhelmingly support comprehensive and enforceable background checks — into the discussion to move Senators to immediately take action to prevent gun violence,” said Bloomberg in a statement released by Mayors Against Illegal Guns.